Mac Payne, 57, was struck in the head by an errant bullet just moments after he exited the train at the South 8th Street stop next to Busch Stadium, according to police.

The shooter was trying to rob a father and son shortly before 11 p.m. inside the train when his gun fired, blasting through a window and hitting Payne. The gunman and five others in his group fled, and the father and son rode on to the Central West End where they were able to contact police.

There were no officers or security guards on the train or platform at the time of the shooting, police say.

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Image via SLMPD

St. Louis police are trying to identify this 'person of interest' as part of MetroLink shooting investigation.

Payne, whose address was listed in the 3700 block of Lindell Boulevard, survived through Sunday night and Monday, but police announced Tuesday that he had been pronounced dead at a local hospital. The case is now considered a homicide investigation. The shooter and accomplices are still on the loose.

Police say the suspects boarded in East St. Louis and panhandled the 51-year-old father and his 29-year-old son. They apparently grew upset when their victims would not give them more money.

Police released a photo on Monday of a "person of interest" in the case.